The present invention relates to a semiconductor integrated circuit having many internal circuits. More particularly, this invention relates to a semiconductor integrated circuit which can realize lower power consumption by driving the internal circuits using a plurality of power supply voltages.
In recent years, lower power consumption of a semiconductor integrated circuit (henceforth, LSI) has been demanded in association with enhanced performance of mobile equipment. As a conventional LSI that allows low power consumption to be realized, there has been known one that uses a plurality of power supply voltages for circuit groups (internal circuits) of the LSI. FIG. 7 schematically shows a configuration of such a conventional LSI. This LSI 91 comprises a plurality of circuit groups 92 (1) to 92 (n) (where n is an integer), a plurality of power supply external terminals 93 (1) to 93 (n) that receive a plurality of power supply voltages VDD (1) to VDD (n) used for the circuit groups 92 (1) to 92 (n), and an external terminal 94 for a ground.
A plurality of power supplies, that generate a plurality of power supply voltages VDD (1) to VDD (n) used for the circuit groups 92 (1) to 92 (n), are provided outside the LSI 91 in the same number as that of the circuit groups 92 (1) to 92 (n). The power supply voltages VDD (1) to VDD (n) from these power supplies are provided to the circuit groups 92 (1) to 92 (n) via the power supply external terminals 93 (1) to 93 (n) in the same number as the number of the circuit groups 92 (1) to 92 (n).
FIG. 8 schematically shows a configuration of another type of conventional LSI that allows lower power consumption to be achieved. This LSI 96 comprises a plurality of circuit groups 92 (1) to 92 (n), a power supply external terminal 93 that receives a power supply voltage VDD (1), an external terminal 94 for a ground, and DCxe2x80x94DC converters 95 (1) to 95 (nxe2x88x921) used for voltage transformation. One unit power supply is provided outside the LSI 96. The power supply voltage VDD (1) provided from this power supply is provided to the circuit group 92 (1) via the power supply external terminal 93. The DC-DC converters 95 (1) to 95 (nxe2x88x921) in the same number as that of the circuit groups 92 (2) to 92 (n) perform voltage transformation on the power supply voltage VDD (1) to generate power supply voltages VDD (2) to VDD (n), and supply the generated power supply voltages VDD (2) to VDD (n) to the circuit groups 92 (2) to 92 (n).
According to the conventional art, however, when power supply voltages used for internal circuits are input from the outside of the LSI, it is required to provide a plurality of power supplies outside the LSI and also provide a large number of power supply external terminals on the LSI. Therefore, there have been problems, for example, package size is increased due to an increase in the number of external terminals for the LSI and the circuit provided outside the LSI becomes complicated. Further, when DC-DC converters are provided inside the LSI, the same level of voltage is input into the DC-DC converters. However, output voltages are decided on the basis of the input voltages in the DC-DC converters. Therefore, there has also been a problem that a power supply voltage for each internal circuit can not be controlled after manufacturing the LSI and it is impossible to provide a power supply voltage adequate to actual characteristics of each of the internal circuits that differ depending on semiconductor processes or some other reasons.
It is an object of this invention to provide a semiconductor integrated circuit that allows a package to be minimized in size by reducing the number of external terminals in an LSI, simplification of a circuit outside the LSI, and supply a power supply voltage adequate to actual characteristics of each of internal circuits.
According to this invention, a plurality of first power supply units provide power supply voltages to internal circuits, a plurality of delay measurement units measure delays of circuit elements of the internal circuits, and a control unit makes the settings of the first power supply units based on the results of measurements in the delay measurement units to control each of the power supply voltages. Accordingly, the need for providing a large number of power supplies outside the semiconductor integrated circuit and the need for providing a large number of power supply terminals on the semiconductor integrated circuit are eliminated. Further, each power supply voltage can be adjusted based on the actual characteristics of each of the internal circuits.
Further, a storage unit stores a digital value according to the setting by the control unit, and a digital-to-analog converter outputs a power supply voltage corresponding to the digital value stored in the storage unit to the internal circuit. Accordingly, the power supply voltage to be supplied to the internal circuit can easily be controlled.
Further, the control unit determines whether the internal circuit requires high-speed processing, and makes the setting of the first power supply unit based on the result of measurement to control the power supply voltage. Accordingly, the power supply voltage responsive to the operation of the semiconductor integrated circuit can be supplied to each of the internal circuits.
Further, a second power supply unit provides a power supply voltage to the internal circuit when a supply of a power supply voltage by the first power supply unit is stopped. Accordingly, even when the operation of the first power supply unit is stopped, a power supply voltage can be provided to the internal circuit.
Further, the second power supply unit is configured with a PMOS transistor whose source is connected to an external power supply, and whose drain and gate are connected to an output terminal for a power supply voltage of the first power supply unit. Accordingly, even when the operation of the first power supply unit is stopped, a power supply voltage can be provided to the internal circuit.
Further, there is provided an external terminal connected to an output terminal for a power supply voltage of the first power supply unit. Accordingly, it is possible to stabilize a power supply voltage by connecting a capacitor between this external terminal and a ground or to use this external terminal as a monitor for a power supply voltage.
Other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.